Add new league columns

[BlackYps]

Adds support for tracking of veteran players to place them earlier than new players

[codecov]

Codecov Report

Merging #580 (b187b60) into develop (b2eeb1e) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@              Coverage Diff              @@
##             develop     #580      +/-   ##
=============================================
+ Coverage      75.84%   75.85%   +0.01%     
- Complexity      1139     1141       +2     
=============================================
  Files            239      239              
  Lines           3610     3612       +2     
  Branches         231      231              
=============================================
+ Hits            2738     2740       +2     
  Misses           776      776              
  Partials          96       96              

Impacted Files	Coverage Δ
.../com/faforever/api/league/domain/LeagueSeason.java	100.00% <100.00%> (ø)
...faforever/api/league/domain/LeagueSeasonScore.java	100.00% <100.00%> (ø)

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[bukajsytlos]

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